Child of constraint not working for two handed object holding
Ok so I fixed it myself.
The problem was in the arm rig and how i setup the IK.
my arm rig didn't have any separate IK bone so i was setting-up the ik on the actual rig.
what i did to fix it was :
1- created a bone from wrist of hand and named IK.Arm.Handle
2- separated the wrist bone and offset it to the IK bone
3- then put the IK constraint on the arm with IK.Arm.Handle target
4- after that i simple put the child of constraint on the IK bone and set target to the object bone ( in my case was sword handle bone ).
I hope helps anyone facing the same issue.